Carpal Tunnel Syndrome (“CTS”) is a condition resulting from the compression of the median nerve that travels through an area in carpus of the hand between the carpal bones and a ligament known as the flexor retinaculum. The compression results in numbness, tingling, weakness in the grip, and pain. CTS produces pain and paresthesia in the arm and often-referred symptoms to the shoulders and neck.
There are many theories as to the causes of CTS. Some believe that it results from irritation of bursa, tendon sheaths, and nerve causing tunnel swelling from repetitive motion. Others attribute CTS to carpal fractures or arthritic joint changes. Still other schools of thought attribute CTS to systemic disease, mechanical stress, or traumatic dislocation. The compression theory that is widely accepted holds that irritated and inflamed tissue resulting from these events within the carpal tunnel compresses the median nerve within the confined space formed by the flexor retinaculum and the carpal bones. Discussion will later allude to the order of events rather than questioning the different perspective. The vast number of cases of CTS is generally believed to be due to repetitive motion.
Traditionally, approaches to treating CTS may be classified as being either conservative or surgical. Surgical treatment of CTS may include open resection of the flexor retinaculum, arthroscopy, and other invasive procedures. Although the surgery is often used as a first line of treatment especially in workers compensation cases, the treatment is permanent and often not effective in the end. The result of surgery often results in return of some symptoms within five years according to the U.S. Bureau of Labor Statistics and patients may incur a lifetime of dysfunction due to scar pain and weakness.
Conservative treatment may consist of rest; steroid injection; application of heat, ultrasound, or phonophoresis to the carpal area; exercising the hand through squeezing putty or tennis balls; or splinting of the carpal area through either static or dynamic means. Steroid injection is often the drug therapy of choice, but this therapy is limited in the number of times it may be applied, may cause serious complications, and demonstrates poor long term resolution of symptoms. Immobilization of the wrist through static wrist splinting prevents movement in one or more planes of motion. U.S. Pat. No. 6,106,492, issued to Darcy, discloses a carpal tunnel splint with a rigid outer shell that immobilizes the wrist while applying pressure upon the metacarpals. Wrist braces and splints that utilize such immobilization address the conventional thought that repetitive or perhaps any motion will exacerbate the pressure on the median nerve and thus the symptoms of CTS. Static wrist splinting is the practice of applying a constant pressure to the wrist, hand, and/or arm regardless of its position or motion. U.S. Pat. No. 5,921,949, issued to Dray, discloses a device that compresses each side of the carpal tunnel and turns or twists each side to the anterior midline, using static pressure to accomplish its result.
Static splinting of the carpal joint has a number of disadvantages. First, such splints are uncomfortable which reduces patient compliance in wearing the splint. Second, by limiting the range of motion of the patient's hand, static splints limit the type of work the patient can do and interfere with the normal activities of daily living. Third, they have been shown to provide relief from the CTS symptoms for only a limited time and documented complications from extended immobilization are common.
Another approach to treating CTS has been to statically restrain pronation and/or supination with a heavy wire rather than a splint. U.S. Pat. No. 5,868,692, issued to Michniewicz, discloses such a device that restricts a user's pronation and supination to 10°, thus preventing extreme torsion that the inventor believes to aggravate those patients with prior arm and wrist injuries. Michniewicz does offer a more comfortable and less confining device than some of the other static splints, but still does not address the underlying causes of CTS.
Dynamic splinting in the traditional sense has heretofore sought to range the wrist through common planes of motion and reduce movement in some planes of motion to reduce irritation to the median nerve. Several devices are illustrative of this dynamic splinting approach. U.S. Pat. No. 5,653,680, issued to Cruz, discloses a device that dynamically controls flexion, extension, ulnar, and radial deviations with adjustable damping springs and appears to effectively limit active range of motion. The device applies rotational force to the wrist joint while pressuring to the second and third metacarpal bones, the pressure promoting a volar or dorsal transrelocation of the distal carpal row. By concentrating on the distal carpal row, Cruz places importance on independently pressuring a region removed from the carpal complex. Cruz further concentrates on the damping aspect of the invention, which is primarily directed to protect the joint against injuries due to shock than to prevent or correct a CTS condition. U.S. Pat. No. 5,413,553, issued to Downes, describes another device called a Carpal Tunnel Mitt that concentrates a mechanical opposition upon the 1st to 5th metacarpal-phalangeal region. The Carpal Tunnel Mitt is structured to deepen the carpal tunnel for decompression purposes and is distal to the actual flexion-extension mechanics occurring at the radio-carpal and mid-carpal region.
CTS and its related disorders are responsible for very high corporate overhead in terms of lost productivity, worker's compensation, and related medical costs from having to subsequently treat the condition that often becomes chronic due to the traditional paradigm of CTS diagnosis and treatment.
As can be seen, there is a need for an orthotic appliance that more precisely addresses the root causes and symptoms of CTS. There is a further need for the orthotic appliance to be inexpensive and easy to fit and use by a layperson. The appliance should be co-dynamic; that is, it should work cooperatively with the hand and carpus to achieve the therapeutic result of correcting a CTS condition. It should allow the hand and wrist to move functionally in all planes of motion so as not to interfere with the normal activities of daily living and to thereby correct the underlying causes of what becomes an inflamed condition leading to carpal tunnel compression.